Salvinia molesta (aquatic plant, herb)
Location Specific Management Information
Preventative measures: Legislation in Australia prohibits the importation of all species of the genus Salvinia (under commonwealth quarantine legislation). The 2000 National strategic plan for salvinia identified prevention strategies (including public education) as the most effective way of managing any invasive weed. The prevention of the trade of salvinia is targeted as an area of improvement, with possible strategies including an enquiry into the effectiveness of the current legislation and an attempt to limit the demand for S. molesta by encouraging the aquatic community to use similar (but non-weedy) aquatic plant species as alternatives to salvinia. To minimise the impact of salvinia in areas where it is already established integrated biological control was emphasised as the best strategy. In addition, local agencies should be encouraged to close or restrict assess to infested waterways to limit spread of the weed.
Biological: The first ever use of C. salviniae to control S. molesta occured in Lake Moondarra (northern Australia) in 1980. Within a year the 200 ha infestation had been destroyed. The average time needed to control an infestation in Australia using C. salviniae is estimated to be between 2 and 4 years (Room et al. 1981; Forno, 1985; Thomas and Room, 1986, in Room and Fernando, 1992). Queensland local government authorities keep breeding tanks of C. salviniae to assist with infestations in the region. The Queensland local government has produced a facts pest series sheet for salvinia outlining ways in which the public can limit the spread of the weed. Brisbane City Council (BBC) and Redlands Shire Council maintain pools for breeding of C. salviniae. The Far North Coast County Council (NSW) has three collection sites. A pyralid moth (Samea multiplicalis) has been trialed as a biological control agent in Lake Julius (Queensland) but did not effectively control the weed (PIER, 2003).
Physical: Manual removal of the weed is only carried out to alleviate water blockages in the short-term, and not as a permenant solution. This is because re-infestation is certain and the cost of manual control is high. Habitat modification is a useful strategy in modified areas or areas in which the use of herbicides is unacceptable. It is not appropriate for environmentally unique areas. Damns, man-made lakes, canals and other water bodies can be drained (or the water level reduced) to strand and dry out the salvinia.
A biological control programme for S. molesta was undertaken simultaneously with programmes for the other aquatic invaders Eichhornia crassipes, Pistia stratiodes and Hydrilla verticillata, to avoid the increase of other invasive species as one was controlled.
The role of contaminated equiptment associated with water activities in encouraging the spread of salvinia has been recognised in Botswana and strict inspection of boats and tailers has been instigated (Howard and Harley, 1998). C. salviniae has also been used successfully to control S. molesta in the country.
Eradication commenced several months after the detection of Salvinia molesta. Hand removal from the pond was followed by herbicide application.
The weevil C. salviniae has been used successfully to control S. molesta in Fiji.
Kakadu National Park
S. molesta had been eradicated from a total of five creeks and river systems by the early 1980s. All existing infestations are currently under adequate control by C. salviniae. Monitoring of the Cyrtobagous/Salvinia system with an emphasis on integrated biological and chemical control is being undertaken at Mission Hole on the Daly River, and in Kakadu National Park (ARMCANZ, 2000). Recommended measures for longterm control of salvinia on the Magela floodplain involve the continued use of weevils in conjunction with herbicides, restricted access, and mechanical harvesting (Finlayson 1994, Storrs & Julien 1996, in Gardner and Finlayson, 2002).
Integrated management: The Australian Nature Conservation Agency (ANCA) and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) are participating in an integrated management project to control S. molesta in the Kakadu National Park, as outlined below:
Biological: Initial release of the beetle C. salviniae occured in 1983. In the Magela creek system the weed continued to spread for several years and the weevil population did not expand. It was reported that control failed (despite being successful at nearby sites), due to high temperatures, which were hypothesised to negatively impact the beetle population (Miller and Wilson, 1989, in Room and Fernando, 1992). Since then studies have futhur characterised the climatic conditions that affect the growth and establishment of C. salviniae in this region. In general conditions unfavourable to the beetles are either (i) a late wet season followed by flooding, or (ii) a poor wet season (either absent or halted). In these cases the following additional control measures are implemented. An excessive build up of secondary vegetation on salvinia infestations (which prevent the sinking of salvinia mats heavily infested by beetles) may also lead to the need for additional control measures.
Chemical: Herbicide is applied by hand or via boats onto vegetation (AF100 is used against loose floating mats and hexazinone is used against compact mats).
Physical: Floating ropes anchored to the bank are used to reduce the spread of the weed due to water currents. Driving airboats over mats (heavily damaged and blackened by weevils) at the end of the dry season has improved sinking.
Cultural: Access is prevented to infested areas and activities associated with boating, fishing or motor vechicles are restricted. Displays of salvinia (immature and mature) are used to help the public and new staff identify the weed. Information displays aimed at those visiting the park are used to encourage the reporting of infestations to the appropriate authorities.
The weevil C. salviniae was released in May 1991 in Lake Naivasha and by mid-1995 the weed had become a rarity in most parts of the lake and fringing wetlands. Although water hyacinth (E. crassipes) has partly invaded areas previously inhabited by salvinia, it is not as well adapted to the environment of the lake, which contains dissolved salts and is exposed to low night temperatures.
The weevil C. salviniae has been used successfully to control S. molesta.
The weevil C. salviniae has been used successfully to control S. molesta in this country (Room, 1986; 1990, in Room and Fernando, 1992)
New South Wales
Due to the difficulty of herbicide control (because of the issues of water contamination and effectiveness), more people are experimenting with biological and physical control methods. Biological control produced reasonable results north of Coffs Harbour. In New South Wales it is estimated that C. salvinae saved A$100 000 (US$77 000) worth of chemical and physical control per annum. At the moment manual control in most situations is difficult, costly and inefficient, requiring on-going follow-ups. Despite all efforts salvinia is still a common plant in the aquarium industry. It still can be found in nurseries and aquarium shops, particularly in the larger urban centres.
Champion and Clayton (2000; 2001a, in Champion, Clayton and Rowe, 2002) designed an aquatic plant weed risk assessment model for New Zealand based on invasiveness level, potential distribution and potential impact; using this model S. molesta was rated 57 (or the 16th highest priority of a total of 36 species rated). The Biosecurity Act (1993) allows for the development of Pest Management Strategies (PMS) at either a central government level or a regional level. These are known as National Pest Management Strategies (NPMS) and Regional Pest Management Strategies (RPMS), respectively. Despite the apparent moderate rating of S. molesta it is among only five weeds nominated by MAF for the development of an NPMS. Two other aquatic weeds have also been targeted by MAF: water hyacinth and water lettuce (Pistia stratiotes).
Papua New Guinea
The weevil C. salviniae has been used successfully to control S. molesta in Papua New Guinea; although the impact of salvinia was catastrophic, it now only causes occasional localised problems. The average time needed to control an infestation of S. molesta using C. salviniae is estimated to be between 1 and 2 years in Papua New Guinea (Pieterse et al, 2003; Thomas and Room, 1986, in Room and Fernando, 1992).
The weevil C. salviniae has been used successfully to control S. molesta.
QueenslandWe are experiencing technical difficulties and unable to complete your request. Please try later.
Integrated management: Priority for control in Queensland is in the Murray-Darling and Lake Eyre catchment since these areas currently contain small infestations (which have the potential to expand considerably). Isolated infestations (such as in the Dawson River and in Banana Shire) should be controlled to prevent spread into salvinia free systems. Brisbane City Council keeps a population of salvinia in order to raise C. salviniae for the annual control of infestations. Some northern shires also carry out dispersal of this agent, although most infestations are flushed into the sea by annual floods. Total eradication of salvinia from Queensland is not practical or feasible. A reduction in the rate of spread of salvia is, however, realistic. Enforced control (including biological, chemical and physical removal) is required for isolated infestations up-stream of clean water bodies and in the Murray-Darling catchment.
Preventative measures: The Queensland Government recently published a salvinia facts sheet (in a pest series) to educate the public on the best ways of controlling and limiting the spread of the weed. It recommends that C. salviniae be released in the spring in warm sunny positions with a high density of salvinia not affected by drops in the water level (which would leave the plants stranded).
Chemical: Herbicides registered for use against the weed are listed and include: AF-100 (calcium dodecylbenzene sulphonate, orange oil with surfactant (not for use in natural waterbodies) and diquat (Vegetrol, Watrol or Reglone®).
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